Fluctuating asymmetry and its relation to cognitive function

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Abstract

Individual variation in cognitive function may be the outcome of developmental instability (DI) as indexed by Fluctuating Asymmetry (FA: departure from bilateral symmetry in traits which are symmetric at population level, such as finger lengths). FA has previously been shown to be negatively related to g-loaded measures of intelligence, but no previous research has investigated the relationship FA may share with other cognitive faculties, such as working memory, short term memory and frontal function. In a population of 30 males and 50 females, four indices of FA were calculated. The study assessed the relationship that these FA indices would share with scores on the g-loaded verbal comprehension and spatial object assembly sub-tests of the Multidimensional Aptitude Battery-II (MAB-II), the automated operation span (Aospan) test of working memory, a forward digit span test of short term memory, and a Frontal Systems Behaviour Scale (FrSBe) questionnaire assessing frontal function. Scores on the spatial MAB-II object assembly test were found to be negatively associated with one of the indices of FA (finger length FA), with a correlation of -.338. None of the other cognitive measures showed significant relationships with any of the indices of FA. Two explanations for the findings are discussed. First, g may be what drives the relationship between FA and cognitive tests, and the g-loading of the non-intelligence tests may not have been sufficient to produce an association. Second, spatial abilities may be primarily linked to FA, with low FA resulting in improved spatial abilities, perhaps coming at a trade-off of verbal ability. Limitations of the present research and other FA research are discussed, along with future directions for the field.